1 files changed, 100 insertions, 0 deletions
diff --git a/lib/ppc/fixtfdi.c b/lib/ppc/fixtfdi.c
new file mode 100644
index 000000000..c95241701
--- /dev/null
+++ b/lib/ppc/fixtfdi.c
@@ -0,0 +1,100 @@
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// int64_t __fixunstfdi(long double x);
+// This file implements the PowerPC 128-bit double-double -> int64_t conversion
+
+#include "DD.h"
+#include <stdint.h>
+
+uint64_t __fixtfdi(long double input)
+{
+	const DD x = { .ld = input };
+	const doublebits hibits = { .d = x.hi };
+	
+	const uint32_t absHighWord = (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff);
+	const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000);
+	
+	// If (1.0 - tiny) <= input < 0x1.0p63:
+	if (UINT32_C(0x03f00000) > absHighWordMinusOne)
+	{
+		// Do an unsigned conversion of the absolute value, then restore the sign.
+		const int unbiasedHeadExponent = absHighWordMinusOne >> 20;
+		
+		int64_t result = hibits.x & INT64_C(0x000fffffffffffff); // mantissa(hi)
+		result |= INT64_C(0x0010000000000000); // matissa(hi) with implicit bit
+		result <<= 10; // mantissa(hi) with one zero preceeding bit.
+		
+		const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63;
+		
+		// If the tail is non-zero, we need to patch in the tail bits.
+		if (0.0 != x.lo)
+		{
+			const doublebits lobits = { .d = x.lo };
+			int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
+			tailMantissa |= INT64_C(0x0010000000000000);
+			
+			// At this point we have the mantissa of |tail|
+			// We need to negate it if head and tail have different signs.
+			const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63;
+			const int64_t negationMask = loNegationMask ^ hiNegationMask;
+			tailMantissa = (tailMantissa ^ negationMask) - negationMask;
+			
+			// Now we have the mantissa of tail as a signed 2s-complement integer
+			
+			const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
+			
+			// Shift the tail mantissa into the right position, accounting for the
+			// bias of 10 that we shifted the head mantissa by.
+			tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10)));
+			
+			result += tailMantissa;
+		}
+		
+		result >>= (62 - unbiasedHeadExponent);
+		
+		// Restore the sign of the result and return
+		result = (result ^ hiNegationMask) - hiNegationMask;
+		return result;
+		
+	}
+
+	// Edge cases handled here:
+	
+	// |x| < 1, result is zero.
+	if (1.0 > __builtin_fabs(x.hi))
+		return INT64_C(0);
+	
+	// x very close to INT64_MIN, care must be taken to see which side we are on.
+	if (x.hi == -0x1.0p63) {
+		
+		int64_t result = INT64_MIN;
+		
+		if (0.0 < x.lo)
+		{
+			// If the tail is positive, the correct result is something other than INT64_MIN.
+			// we'll need to figure out what it is.
+			
+			const doublebits lobits = { .d = x.lo };
+			int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
+			tailMantissa |= INT64_C(0x0010000000000000);
+			
+			// Now we negate the tailMantissa
+			tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1);
+			
+			// And shift it by the appropriate amount
+			const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
+			tailMantissa >>= 1075 - biasedTailExponent;
+			
+			result -= tailMantissa;
+		}
+		
+		return result;
+	}
+	
+	// Signed overflows, infinities, and NaNs
+	if (x.hi > 0.0)
+		return INT64_MAX;
+	else
+		return INT64_MIN;
+}